Abstract

Benthic foraminifera are dominant members of tb meiofauna, commonly occurring below the anoxic-oxic interface in marine sediments. The absence of oxygen in marine coastal sediments is often correlated with the formation of hydrogen sulphide. In this study the tolerance of benthic foraminifera (from the northwestern Adriatic Sea) to hydrogen sulphide was examined experimentally. Although the foraminiferal assemblage exhibited a high tolerance to short-term exposure (21 d), prolonged exposure to sulphidic conditions (66 d with a final concentration of 12 mu M dissolved hydrogen sulphide) resulted in a significant reduction of total foraminiferal densities with time. Reproduction was evident under oxic conditions but none of the genera proliferated under sulphidic conditions. This implies that tolerance of sulphidic conditions was restricted to survival and that sulphide may be a prominent distributional factor for benthic foraminifera. [KEYWORDS: hydrogen sulphide; meiofauna; foraminifera; laboratory experiments Macoma-balthica bivalvia; northern adriatic sea; pore-water oxygen; differential response; thiobiotic meiofauna; subsurface activity; continental-margin; body-size; sulfide; microhabitats]